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  Bearing stiff plate pedestalRelated Patent Categories: Bearings, Rotary Bearing, Plain Bearing, Mounting Or SupportThe Patent Description & Claims data below is from USPTO Patent Application 20060140525. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] The present invention is an improvement over the device and method of application Ser. No. 10/782,212, filed Feb. 19, 2004, a division of application Ser. No. 10/172,899, filed Jun. 17, 2002, now U.S. Pat. No. 6,712,516, hereinafter sometimes referred to as the '516 patent, the specification of which, identical to that of application Ser. No. 10/782,212, is incorporated herein by reference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not Applicable BACKGROUND OF THE INVENTION [0003] In recent years, there has been a concerted effort on the part of the managements of electrical generating stations to upgrade the steam turbines in many older steam turbine-generator units across the United States and elsewhere. There are two directions, generally, to pursue: (1) Upgrading the steam path components such as the vanes (buckets, blades) on the rotors and/or vanes (partitions) in the stationary components (diaphragms, blade rings) while leaving the existing rotors and shells in place, and upgrading adjacent components such as bearings, and (2) Replacing the existing rotors and shells with upgraded rotors and shells, and replacing adjacent components such as bearings with upgraded bearings. In almost all situations, these upgraded designs result from the use and application of advanced technology that is dependent upon the use of digital computers that were not available when the original steam turbines were designed and built. [0004] A major objective is to maintain tight seal clearances in the steam path in order to improve the steam path efficiency. This requires low amplitude rotor vibrations, which can only result from optimized rotor-bearing dynamics for the turbine rotor and bearings. [0005] Since the beginning of the turbine-generator industry, there has been significant pressure to improve the rotor vibration measuring instrumentation and to improve the calculation capabilities for predicting the vibratory characteristics of the rotors in rotor-bearing systems. In the 1940s and 1950s, the instrumentation was rudimentary at best. For rotor-dynamics and film bearing design, the fundamental equations were known, but only the simplest of equations could be solved with the "closed form" analytical methods. With the introduction of digital computers, rotor-dynamics and film bearing designs for systems other than the simplest could be calculated. As the digital computer technology advanced, larger and more complex rotor-bearing-foundation models could be modeled. The results of computer simulations demonstrate the importance of controlling the stiffness of foundations for film bearings for various steam turbine rotors. At the same time, the introduction of solid-state electronics, and then later, the introduction of computer-based instrumentation and diagnostics provided great advances in the ability to monitor, diagnose, and record vibrations of turbine rotors under a wide range of operating conditions. [0006] The results of almost all of the rotor-dynamic studies of a class of large steam turbine rotors known as "high-pressure steam turbine" rotors clearly show that very stiff pedestals for the oil-film bearings that support these rotors is highly advantageous for minimizing the vibratory amplitudes of the rotors relative to the turbine shells. The vibratory instrumentation and equipment for monitoring, diagnosing, and recording the vibrations of these rotors confirms these results. Because there is great value in optimizing the efficiency, availability, and reliability of these steam turbines and their associated generators, there is considerable justification to improve the design of components when and where possible. [0007] This invention has particular application to the replacement of flexible bearing supports of a type used in Westinghouse Electric Company steam turbines from the late 1940s to the mid 1960s, but its utility is not confined thereto. [0008] These original bearing and support arrangements were simple, comprising a yoke, a bearing mounted in a yoke, a bearing cap to retain the bearing in the yoke, and two flexible I-beams to support a yoke. In this type of steam turbine, the bearing design is typically steel backed, Babbitt lined, oil film lubricated, and not of rolling element design. To change the alignment of the rotors it is necessary to change the position of the bearings supporting the rotors. Shims are used between the yoke and pedestals to adjust the vertical height of the yokes and bearings, and jack screws or shims are used to adjust the horizontal positions of the yokes, and hence, of the bearings. This design is discussed in considerable detail in my U.S. Pat. No. 6,712,516. [0009] In the original arrangement, when a turbine rotor with a total weight on the order of 30,000 lbs (133,440 Newtons) is placed in two bearings of this design, the vertical displacement downward of each bearing is approximately 0.003 to 0.005 inches (0.229-0.635 millimeters). This provides a vertical stiffness of the bearing and flexible support on the order of between 5 million lbs/inch (15,000 lbs/0.003 inches) and 3 million lbs/inch. On the other hand, a vertical stiffness of the bearing support of at least 15 million lbs/inch is required to obtain superior rotor-dynamic characteristics, and even higher vertical stiffnesses of the support structures for the film bearings are preferred. [0010] One object of this invention is to provide a method to replace an existing yoke and mating flexible supports with a substantially stiffer pedestal. [0011] Another object of this invention is to provide improved means for aligning the bearing and rotor. [0012] Other objects will occur to those skilled in the art in light of the following description and accompanying drawings. [0013] It should be noted that from the perspective of improved rotor-dynamics, another class of bearing support pedestals exists that is superior to the original spring plate pedestals that are being replaced by the stiff pedestal of this invention. This other class of bearing support pedestals uses heavy steel plates welded into, and therefore, integral with, the outer pedestal housings. It has been used by all manufacturers of turbines for at least as long as the spring plate pedestal has been used, and is satisfactory for providing adequate stiffness for the oil film bearings used. Upgraded pedestals using the stiff pedestal design and methods of this invention are comparable in stiffness to this other class of bearing pedestals that were welded into and integral with the outer pedestal housings. BRIEF SUMMARY OF THE INVENTION [0014] In accordance with this invention, generally stated, the original bearing, yoke and two spring plate pedestals are removed from the base of the outer pedestal housing, and are replaced by stiff plate pedestals and new bearings, with each stiff plate pedestal being made from a single heavy plate of steel with a cylindrical bore and with two mounting feet machined into the plate, such that the mounting feet seat onto the base of the outer pedestal housing in approximately the same locations from which the original spring plate pedestals were removed. The removal of the original spring plate pedestal can be the result of breakage of the plate, as described in patent '516, or by burning or machining off the original spring plate. The replacement can be accomplished as described in that patent or in an analogous method here described, or by removal of a flexible plate of patent '516. The new bearing comprises (a) a lower half bearing housing, with shimmed saddle blocks that have a cylindrical outer surface, that mates to the cylindrical bore, or saddle, of the new pedestal, (b) an upper half bearing housing with ears having gaps between the ears and the top surface of the new stiff pedestal, (c) shims that almost fill these gaps, (d) bolts to hold down the ears and shims to the stiff pedestal, (e) Babbitted tilting pads to form a bearing to mate to a journal of the rotor, the Babbitted pads each having a self-alignment feature to permit the journal to maintain alignment in the form of tilting and twisting to the journal at all times, including during rotor vibrations and during thermal changes of diameter. The shims associated with each saddle block and the gaps between the ears and the pedestal permit precise alignment of the bearing and rotor as required by the rotor and turbine shell assembly. [0015] If the original spring plate pedestals were welded into the base of the pedestal outer housing, these are cut away, and, in the preferred embodiment, new mounting surfaces are machined onto the base of the pedestal surrounding the original spring plate pedestals. A bolt pattern is drilled through the mounting feet of the new heavy plate pedestal. During installation, the stiff plate pedestal is aligned to its approximate final vertical, horizontal, twist and tilt positions by any one of several methods, with the bottom surfaces of the stiff plate pedestal plate being machined to establish proper elevation and tilt of the saddle bore relative to the anticipated journal position and orientation, and then holes are transferred to the base of the outer pedestal housing, the bolt pattern in the mounting feet serving as a template or drill fixture, the new pedestal plate is removed, the bolt holes are drilled and tapped, the work area is cleaned up, the new pedestal is aligned with precision, and it is assembled and bolted into place. [0016] In the method of replacing a welded bearing flexible support plate with a stiff plate pedestal, there are three preferred methods, all counterparts to the three methods set out in patent '516. In the first, after removing the bulk of each vertical flexible plate, any part of the flexible plate protruding from the base plate of the outer pedestal housing is machined, as by milling or grinding off with a portable milling machine or grinder, both methods being encompassed by the term "machined" as used herein, and that part and the top surface of the base plate surrounding it are machined so that they are flat, and this top surface of the base plate now becomes the mating surface to the replacement stiff bearing support plate. It is preferred that the two mating surfaces machined into the base plate be machined in the same plane, but this is not required as the two mating surfaces of the bottom of the new stiff pedestal can be machined individually as required to set properly onto the mating surfaces of the base plate. In certain cases, it may be possible to machine one continuous mating surface into the base plate. [0017] The new stiff plate pedestal with mounting holes already drilled, is positioned over the exposed surface of the pedestal base in precisely the position to be assumed in final assembly, holes are drilled in the pedestal base in conformance with the hole pattern in the heavy plate pedestal, and tapped. A common method of making the holes in the new stiff plate pedestal for use as a drill fixture is to make the diameters of the holes to be the diameters of the tap drills to be used to make the holes in the base plate of the outer housing, and not the diameters of the clearance holes that will be used during final installation. If epoxy is used to help secure the bottom surfaces of the stiff plate pedestal to the pedestal base and to fill any voids that might be found between the mating surfaces block, it is applied just before the stiff plate pedestal is assembled to the base plate. Then the stiff plate pedestal is installed, and then the hold-down bolts are installed and torqued. [0018] In a second method, any remaining portions of the flexible plates are machined down so that they protrude a short distance, as, for example, approximately 1/4 inch, but are not completely eliminated. The surface areas around the protruding flexible plates are machined flat, preferably leaving a narrow strip, for example, about 1/16th of an inch per side, of unmachined surface around the protruding flexible plate stub or stubs, contiguous the protruding flex plate stub. A groove sufficiently deep to accommodate the protruding flexible plate stub, and wide enough to bridge the distance beyond the inner edges of the machined strips is machined into the bottom surface of the stiff plate pedestal. Epoxy can be used to form a permanent chock in the gaps around the remains of the protruding flexible plates, and any other gaps between the bottom surfaces of each of the mating surfaces of the stiff plate pedestal and the tops of the mating sections of the base plate of the outer pedestal housing. The method of using the stiff plate pedestal as a drill fixture as described in the first method above is common to all the methods in the preferred embodiments. [0019] The third method is to grind the broken and protruding remains of the original flexible plates and to leave them protruding for a short distance, as, for example, 1/4 of an inch, and not to machine flat the mating surfaces of the base plate. The stiff plate pedestal, with grooves in the bottom surface, is used as in the prior two methods, but the two bottom mating surfaces of the stiff plate pedestal are not expected to sit flatly on the top surfaces of the pedestal base plate. The stiff plate pedestal is supported by a block, shim, small jack screws or otherwise so that it remains located and oriented properly throughout the installation process. The stiff plate pedestal is used as a drill fixture as in the other two cases to locate and drill the hold-down bolt holes. In this case, epoxy is used to form a permanent chock in the gaps around the remains of the protruding flex plates and other gaps between the bottom of the stiff plate pedestal and the top of the mating sections of the pedestal base plate. Once the stiff plate pedestal is bolted in place and the epoxy is suitably cured, then the assembly of the bearing and turbine rotor can proceed. [0020] In any of the above methods for installing the stiff plate pedestal, it is essential to align the cylindrical bore, or saddle, of the stiff plate pedestal so that is approximately concentric with the anticipated orientation of the respective journal of the turbine rotor when the rotor is installed. This means that the centerline of the saddle bore of the stiff plate pedestal must be in the approximate horizontal and vertical position, and the centerline of the saddle bore must have the proper twist (angle in the horizontal plane) and tilt (angle in the vertical plane). Continue reading... Full patent description for Bearing stiff plate pedestal Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Bearing stiff plate pedestal patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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